Sodium Metabisulfite, 98%
Synonyms: Pyrosulfurous acid, disodium salt; Sodium Pyrosulfite; Disodium Salt Pyrosulfurous Acid; Sodium disulfite; Disodium disulfite; Disulfurous
Grade: Food Grade, fine crystal
Uses: preservative, antioxidant, bleaching agent.
Old Code: S025
Sodium metabisulfite (SMBS) is commonly used for removal of free chlorine and as a biostatic. Other chemical reducing agents exist (e.g., sulfur dioxide), but they are not as cost-effective as SMBS. When dissolved in water, sodium bisulfite (SBS) is formed from SMBS: Na2S2O5 + H2O --> 2 NaHSO3 then reduces hypochlorous acid according to: 2NaHSO3 + 2HOCl --> H2SO4 + 2HCl + Na2SO4 In theory, 1.34 mg of sodium metabisulfite will remove 1.0 mg of free chlorine. In practice, however, 3.0 mg of sodium metabisulfite is normally used to remove 1.0 mg of chlorine.
Toxic by inhalation. Tolerance, 5 mg per cubic meter of air.